Adjustable resistance unit



C. E. STRYKER.

ADJUSTABLE RESISTANCE UNIT Filed Oct. 21. 1925 e mwa GLNTONE. STBYHER, MOR-TH CHICGO, ILLINOIS, ASSIGNOR TO FANSTEEL PROD- COMEANY, ING., OF OBTH CI-ICAGO, ILLNOIS, A COEPORATION OF NEW YORK.

ADJ'USTABLE EESISTANCE UNIT.

Applcaton filed 'October 21,*1925. 'Serial NOJG3B32.

Myiuventon relates to a djustable electrcal resstance devices such as those 'used in rail-way battery .and signal creuts, and

generally in electrical circuits where an adjustable resistance is required where the adjustments are to be maintainedtor'a considerable period ot time, and where :devices may be subject to jars and vibrations.

. The object of my nvention istouprovide an adjust-able resistanceunit w h a small number of parts, which is simple' 'in construction and can becheaply manutactured.

&further object is to provide aresistance de' ice in which adjustment o't'the 'resistance may be quickly and easily made.

A further object is to provide anadjustable resistance unit which is adaptedto be readily inserted and removed from'an electrical circuit.

A further'object is to provide acomparatively rigid support tor an adjustable contact so that relatively great pressure may be exerted to firmly hold the contact member against the resistance wire.

A further object is to provide an improved contact element which is easily made and assembled.

Other objects will appear 'from the :tollowing description, reference being made to the accompanying drawings in which:

Fig. l is an end elevation of the improved resistance device.

2 is a longrudinal vertical sectional view o't the device taken on the line 2-2 of Fig. also showing how the same may be Suite connected to a panel boarc.

F ig. 3 is a transverse vertical sectional view ot the device taken on the line 3 3 ot Fig. 4.

Fig. et is a plan view ot the device.

The block or body portion 1 ot the resistance device keystone shaped so as to be easily molded of porcelain or any other suitable nsulating material. Tt has suitable pedestals 2 which are slotted as at 3 to provide passages tor the resistance The block is grooved on three sides to receive the resistance wire et which is wound around the block in the usual manner. These grooves are so formed that the contecting portions of the wire lie transversely ot the block on its top or Contacting suriace which is not grooved. The open slotted support braclet 5 fits into a tormed depression in the end ot the block to prevent it from turning, and is secured by the'scre-w 6 which lies iu a hole tormed in block 'the hoie being enlarged for short distance as shown at 7 to receive the head of the screw (3.

in the process ot assembly the brac ket 5 eecured to 'the blocl; l, the r" stance wire attached to this braclret and then wound on the block, and the -l-oose end passed through the slot 3 (shownat the right in Figure: 2) and wound around ic pedestal 2 to prevent ittrem unwinding while the remaining ass' m bly Opera ons are 'being performed. i the peC l 2 with the slet 3 grea'tly 't'ichitates assembly by provic ing a mean 'l t ie loose end of the wire ule n :upon whic i may ue temporarily anchored during the assembly operation.

The contact support 8 is substantially inverted t-shaped and is integra with the other support braclet G The contact support is bridged over the block, fits into depressions tormed in the ends of the block and is secured to the block by means ot the fiatheaded machine screw 9 which extends through the block and at its end is threaded into the downwardly bent portion ot the contact support, thus rigidly fastening it in place. The bridge portion has a tull length longitudinal slot 8 The contact member 10 comprses a strip of slightly resilient conducting material bent so as to have two U-shaped contacting sui-faces and is loosely riveted at its center to the thumb screw ll which extends through and is slidable in the slot 8 T he Contacting surfaces of the member 10 are wide enough to embrace a number of convolutions of the resistance wire as shown in Figure 2, thereby securing a pluraiity of points of contact to insure good electrical connection with the resistance wire. The contact member 10 has upwardly projecting ends 10 which extend through suitable slots in the guide 12. These ends by their engagement with the sides of the contact support 8 maintain the contact member in substantially transverse position. The screw ll is fitted with a suitable thumb nut 13 by means of which the contact memb s may be clamped in the desired adjusted position along the contact support 8. The resistance wire is sutably connected, preferably soldered, at one end to the bracket 5 and at the other to the bracket S It will be seen that by moving the contact member to the right (Figs. 2 and 4) the resistance n the circuit may be increased While by moving it to the left the resistance may be decreased.

. The resistance unit may be secured to panel board or other suitable support lt by means of the screws 15 and the nuts 16, 17.'

The wire connectons to the unit are made in the usual manner by tightening the thumb screws 18 over the connecting Wires. Due to the disposition of the open end slots in the support brackets 5 and B the unit may be detached from the panel by merely loosening the thumb screws 18 and the nuts 17.

The invention is capable of variation and adaptation in many respects for use in difr :Eerent embodiments Without departure from vertical depressions, a resilient-contact member and means for holding it in ar fixed position, and means passing through said block and engaging the upwardly and doWnWardly extending portions of' the metal strip to prevent. the block from turning on the bracket and to rigidly hold the contact supporting member. i

2. A resistance unit comprising an insulating block provided With vertical depressions in each end, a resistance Wire Wound on said block, a single metal strip adapted to serve as a bracket support for the block, to fit in the depressions to. prevent rotation of the block, and to form a contact support bridging said block, said contact v support being slotted ho rizontally, a contact member comprising a thumb screw, a slotted guide' and resilient conductin material the latter being Secured to 'the thumb screw, bent i doWnWardly on each side of the screw to contact With the Wire and then bent up- Wardly through the slots in the slotted guide to engage said contactsup'port Whereby the ends ot the resilient member, the slotted guides and the contact support maintain themselves in fixed relative position, and means passing through the metal strip and the insulating block for rigdly holding these elements in position.

In Witness whereof, I hereunto subscribe my name this 9th day of October, 1925. C. E. STRYKER. 

